The present invention relates to a non-asbestos friction material used for the brake lining, disc pad, clutch facing, etc. for cars and industrial machinery.
In said friction material for cars and industrial machinery, solid lubricant is usually formulated in consideration of the stability of friction coefficient and the wear resistance. As these solid lubricants, organic friction dust and inorganic lubricants such as graphite and molybdenum disulfide have been used so far.
For this organic friction dust, it is common to use particles obtainable by polymerizing cashew nut shell oil and particles obtainable by vulcanizing elastic polymers such as rubber. By mixing these with friction material, adequate elasticity is given to the friction material and, as a result, the friction characteristics are stabilized, since the contact area of friction surfaces increases through the elastic deformation on engaging with partner component of friction. Namely, the action of this organic friction dust is considered that, through the fluid or gas lubrication by low-molecular organic ingredients produced by depolymerization due to the frictional heat, the friction characteristics at low temperature is stabilized.
There is a problem, however, that, since the thermal decomposition products become too much and the lubrication becomes excessive at high temperature, so-called fade phenomenon, the friction coefficient being abruptly decreased, is caused resulting in an increased wear, too. Namely, the defect of the organic friction dust of this type lies in only the fade phenomenon, thus, with the friction materials put now into practice, the fade phenomenon and the wear at high temperature are suppressed as low as possible in consideration of the stability of friction characteristics to realize on a balance of both.
In practice, however, there has been a limit for this as long as the organic friction dust is used.
As a result of extensive investigations in view of this situation, a non-asbestos friction material, with which said problem is solved, has been developed according to the invention.